Actually, since MSDN and Technet Members have them now, regardless that they should all be genuine, I'm surprised the genuine website hasn't been updated for remote testing or something for Win7.
I think you'll see the site start working closer to the actual "live" date.They could be working out some issues they ran into heh.
I am using Microsoft Security Essentials on Windows 7 RTM with no problem at all. MSE is by far the best antivirus ever.
Some could agree with you, some - not. Let's stay 'neutral' and state that it's an ok program, that has a good potential. I wouldn't hurry up and make bold statements that it's either bad nor 'the best' before I see it out of beta version.
Basically if you don't go to weird websites or download unknown things you wouldn't really need an antivirus. But who's acting like that on web? No one I think.